In general, an electric device is known, and this electric device configures a system by mutually connecting high-voltage devices such as a high-voltage conductor, a circuit breaker, a disconnector, and a vacuum valve which are molded by a solid insulating material represented by epoxy resin.
In the mutually connected high-voltage devices, the high-voltage device on one side has a connection surface having a convex shape protruding in a conical shape, and has a conductor at the center, and the outer periphery of the conductor is molded by a solid insulating material. The high-voltage device on the other side has a connection surface having a concave shape dented in a conical shape, and also has a conductor at the center, and the outer periphery of the conductor is molded by a solid insulating material.
When current is applied, high voltage is applied to the conductor provided at the center of each high-voltage device. The outer peripheral surface of the solid insulating material forming the mold is often processed so as to be coated with a conductive paint and is electrically grounded.
That is, in the electric device configuring the system, an insulation property is important at the contact interfaces of the solid insulating material (referred to as a one-side solid insulating material) of the high-voltage device on one side and the solid insulating material (referred to as an other-side solid insulating material) of the high-voltage device on the other side. Accordingly, a flexible insulating material such as silicone rubber is interposed between the contact interfaces, to improve the adhesiveness of the solid insulating materials, thus a void and a gap at the interface can be eliminated and the insulation property can be improved.
However, in the case where the solid insulating materials are merely connected with a flexible insulating material interposed therebetween, the surface pressure becomes uneven in the thickness direction, the internal diameter direction, and the external diameter direction in the flexible insulating material, and partial discharge occurs at a part in which the surface pressure is low, thus a problem exists in that the insulation property is deteriorated.
In order to solve such a problem, one of electric devices is configured such that a step portion is provided in the contact surface of the other-side solid insulating material that contacts with the one-side solid insulating material, and the solid insulating materials are connected to each other while a flexible insulating material having a greater thickness than the depth of the step portion is interposed therebetween, thereby the surface pressure of the flexible insulating material can become constant. In this electric device, silicon grease is applied to the step portion (see, for example, Patent Document 1).
In another electric device, the center-side thickness of a soft insulating material corresponding to the flexible insulating material is set to be greater than the thickness on the external diameter side, and in the interface between each solid insulating material and the soft insulating material, the surface pressure on the center side in which the electric field intensity is high becomes greater when the high-voltage device on one side and the high-voltage device on the other side are connected, thus withstand voltage performance can be improved (see, for example, Patent Document 2).